mybatis通过resultMap解决了列名和属性名不匹配，为啥我的属性值出现了null

Question

代码：

@Data
public class Employee implements Serializable{
    private Long id;
    private String name;
    private Long deptId;
}

public interface EmployeeMapper {
    
    Employee get(Long id);
}

<mapper namespace="com.shan.hello.mapper.EmployeeMapper">
    <cache/>
    <resultMap  id="BaseResultMap" type="Employee">
        <id column="id" property="id"/>
        <result column="name" property="name"/>
        <result column="dept_id" property="deptId"/>
    </resultMap>
    
    <select id="get" resultType="Employee" useCache="true">
        select id, name, dept_id from employee2 where id = #{id}
    </select>
    
</mapper>


    @Test
    public void test() throws Exception {
        SqlSession session = MyBatisUtil.getSession();
        EmployeeMapper employeeMapper = session.getMapper(EmployeeMapper.class);
        Employee employee = employeeMapper.get(1L);
        
        System.out.println(employee);
        
        //清空一级缓存
        session.clearCache();
        
        Employee employee2 = employeeMapper.get(1L);
        System.out.println(employee2);
    }

问题：我的deptId是null

Answer 1

“”问题：我的deptId是null“” 是因为你使用的是resultType=“Employee”，默认也是列名和属性名不匹配的，导致你到数据库查询的时候id和name可以查询出来，而deptId跟你的数据库的列名不匹配就查询不出来